88 THE PLANT: A GENERAL INTERNAL VIEW 



Section 25. i. Describe some of the relations between root-hairs 

 and soil. 2. Why is it easier for roots and root-hairs to grow and 

 work in soil which has been spaded or plowed ? 3. Have plant excre- 

 tions anything to do with fertility? Explain your answer. 4. De- 

 scribe the inner structure of a root, defining cortex and stele. 5. De- 

 scribe xylem and phloem. 6. Can you, with a knife, separate the 

 cortex of a young root from the stele ? 7. Why is rigidity an advantage 

 to stems and not to roots ? Why is too much rigidity a disadvantage 

 to stems? 8. What plants have stems which stand erect, and yet 

 bend easily without breaking? 9. What is the vascular cylinder 

 and where is it found? 10. What are vascular bundles? Give ex- 

 amples of vascular bundles you have seen. n. How do trees increase 

 in diameter? 12. Describe the way in which the vascvilar bundles 

 of a corn stem are arranged. 13. What difference is there between 

 water and sap ? 14. Examine a leaf and describe the way in which 

 its veins are arranged. 15. Describe the movement of sap from roots 

 to leaf. 



Section 26. i. Describe the structure of the inside of a leaf as 

 shown by Figure 36. 2. What do the cells of the inside of the leaf 

 take from the air, and what do they give up to it? 3. What is an 

 advantage to the plant in having its stomates on the under rather 

 than on the upper surface of a leaf ? 4. Where would you expect 

 the leaf of a water lily to have its stomates ? Explain your answer. 

 5. Is there more chlorophyll on the upper or under side of a leaf? 

 What advantage in this? 6. What four things are mentioned as 

 necessary to the work of the leaf? 7. Does it appear from their 

 structure that leaves absorb water which falls on them or shed' it ? 

 8. Is it better to sprinkle the leaves of plants or the soil over the 

 roots ? Explain your answer. 



Section 27. i. What conditions are necessary to the sprouting 

 of a seed ? How would you arrange experiments to prove just what 

 conditions are necessary? Are light and soil necessary? 2. What 

 happens when a seed sprouts? 3. Define the term shoot. Can you 

 think of any exceptions to the rule that shoots grow up? Could 

 you place a sprouting seed under such conditions that its shoot 

 would grow down and its roots grow up ? 4. What is pollen ? Name 

 some plant whose pollen you have observed. What color is it ? 

 5. Describe "the working together of the whole machine." 



